Rheostat



Nov. .6 1923. 1,472,914

L. KEBLER RHEOSTAT Filed March 23; 1920 3 Sheets-Sheet l & 0 17 '27 I I Swvwtoz Gamm No v. e, 1923.

1,472,914 L. KEBLER ngzosm'r Filed March 23. 1920 3 Sheets-Sheet 2 L. KEBLER RHEOS'I'AT Nov. 6, 1923.

Filed March 23, 1920 5 Sheets-Sheet 5 mu /4 WW dM,

Patented Nov. 6, 1923.

UNITED STATESPATENT orr cs.

LEONARD KEBLEB, OF BRONXVILLE, NEW YORK, ABSIGNOB TO 'WAfiD LEONARD ELEC- TRIO COMPANY, A CORPORATION OF NEW YORK. i

BBEOSTA'I.

Application filed March 28, 1820. Serial No. 888,108.

To all whom it may concern:

Be it known that l LEONARD KEBLER, a citizen of the United States, residing at Bronxville, in the county of Wcstchester and State of New York, have invented certain new and useful Improvements in Rheo stats, of which the following is a specification.

In general the object of this invention is to provide an improved rheostat or resistance controllensuch for example as a motor starting rheostat and the like, of a simple and durable construction and having comparatively large capacity without" overheating. and of comparatively small size. One special object is to so construct the rheostat that the operating parts may be readily enclosed and to provide enclosing means for such parts and avoid any interference with the rapid dissipation of heat. This enclosure 'of the rheostat is particularly desirable in certain classes of use where the device is exposed to dust, dirt or moisture. Another object is to adapt the construction so that the user may himself readily and simply make the change from the unenclosed to the enclosed form or vice versa. Various special improved features of construction-are also included in this invention, as will appear from the following description and accompanying drawings.

Fig. 1 is a front elevation of one form of my invention with the enclosing casing removed and adapted for use without such casing. Fig. 2 is a horizontal section on the line 2-2 of Fig. 1, but with the enclosing casing adapted for use with the operating parts enclosed. Fi 3 is a vertical section on the line 3-3 0 Fig. 2; Fig. 4 is a side elevation from the right of Fig. 1 with the enclosing side of the resistance units removed and the operating lever removed. Fig. 5 is an enlarged sectional view through the operating arms of Fig. 2 showing their construction and relationship when the rheostat is enclosed. Fig. 6 is an enlarged sectional view of the outer end of the con.- tact arm, and Fig. 7 is an enlarged sectional view on the line 7-7 of Fig. 1 through the initial live contact.

The face plate 10 of the rheostat is preferably formed of molded material having molded therein on its face designations L 1,

l L 2, F 1 and A 1, designating the connections for the line terminals and field and armature terminals of the motor. The face plate also has molded therein perforations for the mounting of the parts and particularly the initial live contact 11. This is preferably a carbon block fitted within a sheet metal strip or carrier 12 as shown in Fi 7, which is of a dove-tail shape and pa'rtia ly imbeoldad in the molded plate 10. The dove-tail sha e of the carrier 12 prevents the contact 11 rom coming out of the carrier, and the walls of the depression in the molded plate 10 prevents the earlier block 11 from moving sidewise out of the carrier 12. It also permits the ready removal of the carbon block by merely disconnecting the carrier from its terminal connection.

The resistance contacts of the rheostat are shown mounted on the face of the plate 10 14, which serves as one pole of the magnet having an extension 14' which cooperates wlth the other pole of the magnet to retain the arm of the rheostat in running position.

This sheet metal part1; also has integral therewith'and bent at right angles thereto an extension 14: along the face of plate 10. This portion of the sheet metal element ex tends under the last two contacts of the rheostat,.which are shown in Fig. 1 as being bolted thereto and having electrical connection therewith. The sheet metal element likewise has electrically connected therewith and mounted thereon a terminal connection A 1 for the armature lead. This sheet metal element will thus be stamped out and then bent to the form shown and servefor mounting the no-voltage magnet, for cooperating magneticall with the rheostat arm, for connecting with the running contacts of the rheostat and also with the armature terminal. This ives a particularly durable construction an one easily and economically manufactured.

The contact arm 15 of the rheostat is shown of channel formation having an upvwardly extending part 15 and a downspring 21' and that The sheet metal plate 17 has an extension to the right for connection of one of the line terminals and has an upwardly turned part 17', serving as a bumper for the contact arm and an upwardly turned part 17" serving as a catch for one end of the spring 18 which tends to return the arm to initial position. The contact arm 15 is retained in place' on the shaft 16 by a spring clip 19 engaging a groove in the upper end of the shaft. The arm is thus readily assembled and removed. The retracting spring 18 is shown coiled about the shaft 16 and has an extension to the right engaging the abutment 17". s The other end of the spring passes to the left out through an opening in the side of the channel shaped arm 15 and is then bent toward the axis of the shaft so as to engage the extension 17. The spring 18 thus serves not only to retract the arm 15. but 'to also engage the bumper 1.7 in initial position. thus serving as a bumper spring as well as a retracting spring.

.ln the channel portion of the contact arm is mounted the spring pressed movable con tact parts of the rheostat. The sheet metal carrier plate 20 has outwardly turned side portions which fit within the channel of the arm and is pivotally connected thereto by a pin 21. Around this pin is a spiral spring 21 as shown in Fig.6 having two spiral portions and a central loop portion pressing downwardly against the pivoted plate 20 and having the outer ends of the spring engaging the under-face of the contact arm. The plate 20 has loosely mounted at its outer end the movable contact 22 which is on the under-face of the metal strip 20 held therefrom by a central boss and has edges 22' bent outwardly to loosely engage the sides of the plate 20. The contact 22 also has outwardly extending edges 22 which engage notches in the plate 20. The contact 22 although having freedom of movement on the outer end of the plate 20 is held loosely in place thereon by this construction. The contact 22 has an outwardly extending tongue passing through a hole 20' in the plate 20 to which the flexible lead 23 is electrically connected. This lead is electrically connected at its other end to the contact arm by nut 24, which is engaged by a central screw for holding the handle 24: of the contact arm in position. It is evident that the movable contact 22 is yieldably pressed against the contacts of the rheostat by the plate 20 and the contact 22 has a self-adjusting freedom of movement to the surface of the contacts so as to secure good electrical connection in all positions of the contact arm.

A soft steel or soft iron plate 25 is riveted on the inside of the contact arm 15 and extends outwardly through the righthand side of the contact arm and is adapted to be engaged by the poles of the retaining magnet 13 when the arm is in running position.

The resistances connected to the rheostat contacts are subdivided into units and made up in a form and mounted in such relationship as to secure a very high degree of heat diss pation and likewise a durable construction which is simple and readily assembled. The resistance is shown as in the form of resistance tube units 26, the units being preferably formed by winding the resistance wire upon a porcelain tube and coated with vitreous enamel. Each of these units 26 has a pair of flexible leads (not shown) for connection of each unit, in circuit to the rheostat contacts in proper relationship.

The rheostat normally stands in a vertical position and the resistance units are mounted spaced from each other and in a vertical position in an enclosing box back of the face plate 10. This box is shown as having a sheet metal back and sides 27. The sheet metal parts 27 have offset outwardly extending feet .27 for mounting the rheostat.

The upper and lower sides 28 of the resistance box are preferably of molded in sulating material. They are shown as having inner recesses 28 for receiving and supporting the ends of the resistance tubes 26 which fit loosely therein. The insulating .plates 28 also have perforations 2S" oppo site the ends of the resistance units so as to give continuous ventilation through the inside of the resistance tube units from the lower openings 28 up through the tubes and out at the upper openings 28". This construction has been found to give very advantageous dissipation of the heat. porcelain being a good heat conductor and thus absorbing the heat from the resistance wires and readily dissipating it from the interior of the tubes. In this construction heat is also dissipated from the enameled exterior of the tubes and passes out through the crevices where the ends of the tube are seated.

The insulating plates 28 are fitted between the side pieces 27 and have notches in their outer edges which are engaged by projecting edges 10 of the face plate. The inner edges of the plates 28 are notched to fit over the back plate of the rheostat box. The ends of the plates 28 are somewhat cut away for the passage of screws 29 as shown in Figs. 3 and 4, these screws ex tending through the face plate 10 and the back plate and engaging nuts 29'. These screws thus hold the parts together and retain the side plates 28 in position. The resistance elements and box are thus con veniently assembled and disassembled and se- 7 cures a rugged and durable construction.

The construction of the rheostat as above described is also ada ted for convenient enclosure of the operating parts when desired without the necessity of any additional drilling. or machine work of any character. To accomplish this, the handle 24 of the contact arm' is removed and a screw 24:

is used for making the connection with the lead 23 as shown in Fig. 5. A sheet metal.

enclosingca'sing 30 fits over the operating parts and is provided .with inwar ly projecting edges 30' engaging the sides of face plate 10. Sheet metal angular strips 30" are riveted to the sides of this casing and have inwardly extending parts which fit over the corners of'the face plate 10 and are perforated for. the reception of the screw 29, although the casing may be held in place by other suitable means.

The casing is provided with a hole through which projects means for connecting the opcrating arm 31 to the contact and. The arm 31 is similar to the contact arm 15 and the handle 24 is now applied to the arm 31. An extension piece 32. preferably of molded insulating material, is shaped to fit over the shaft 16 and outer part of the extension 15' as shown in Figs. 2 and 5. The part 32 has an extension 32 which fits over the inclined portion of the extension 15' and engages its sides. A circular sheet metal plate 33, having an upturned edge 33,wh1ch fits within the inside of the extension 15, encircles the ghaft 16, to the sides of the inclined portion of the extension 15. Screws 34 pass through holes in the flange of the part 32 and engage the metal plate 33 and thus clamp the insulating part'32 firmly to the contact arm. The arm '31 is mounted on and clamped to the outer end of the auxiliary part 32 byscrew 35 as shown in Fig. 5.

The arm 31 and handle 24 when thus connected are in line with and occupy the same relative positions as the contact arm and operating handle when used without the en closing; case and has the same mode of operation. The construction thus avoids confusion to the user which might otherwise 00+ cur with a different relative location of the parts. o

It is thus apparent that the rheostat may be enclosed efiectively and conveniently by the above described construction and that the same general construction of the rheosta't maybe standardized for the enclosed type or the open type which not only gives convenience to the user in making the change when desired, but also permits the manufacturer to utilize the same patterns,

' dies and the like for both types of rheostats.

Although I have described a preferred embodiment of my invention in its various features, it will be understood that modifications may be made without departing from i the scope thereof.

1. In a rheostat, a series of resistance contacts on the facep1ate,.a controlling contact arm, a plurality of resistance tubes back of the face plate, said tubes being of insulating material and having resistance woundthereon, and a pair ofplates opposite the ends of said resistance tubes and having perforations in line with the ends of said tubes. the ends of said tubes being seated in and directly supported by said lates.

2.-In a rheostat, a series 0 resistance contacts on the face plate, a controlling contact arm, a plurality of resistance tubes back of the face plate, said tubes being of insulating material and having resistance wound thereon, and a pair of plates opposite the ends of said resistance tubes and having recesses for receiving the ends of said tubes and also having perforations 'opposite the '-ends of said tubes.'theends of said tubes being seated in said recesses and being directly supported by said plates.

3. In a rheostat, a series of resistance contacts on the face plate, a controlling contact arm, a pluralityof resistance units hack of the face plate, and a box for enclosing and supporting said units, said box com prising a sheet metal back and side portions and upper and lower side portions of insulating material, said portions of insulating material having recesses and the ends' sistance contacts mounted thereon, a contact arm for engaging said contacts successively, a casing engaging the face plate and enclosing sald contacts and arm, an operating handle outside the casing, and removable means connecting said handle to said arm.

6. A rheostat comprising aface plate, resistance contacts mounted thereon 'a contact arm for engaging said contacts successively, a casing engaging the face plate and-enclosing said contacts and arm, an operating handle outside the casing, and means clamped to said arm and connected with said handle.

- 7. A rheostatcomprising a face plate, re-

sistance contacts mounted thereon, a contact arm for engaging said contacts successively, a casing engaging the face plate and enclos ing said contacts and arm, a second arm outside said casing, and means extending through the casing for connecting said arms.

8. In a rheostat, a series of contacts, a controlling arm, at least one of said contacts comprising a metal holder and a block of conducting material carried thereby.

9. In a rheostat, a series of contacts, a controlling arm, at least one of said contacts comprising a metal holder and a block of conducting material carried thereby and sunk in the lace plate of the rheostat.

10. In a rheostat, a series of contacts, a controlling arm, at least one of said contacts comprising a metal holder and a block of conducting material carried thereby, said holder having edges engaging said block to retain it in position.

ii. In a rheostat, a series of contacts, a controlling arm, at least one of said contacts comprising a metal holder and a block of conducting material carried thereby, said holder having edges engaging said block to retain it in position, and said holder and block sunlc in the face plate of said rheostat.

12. In a rheostat, a controllingarm, a magnet for retaining said arm, and a single metal piece for supportin the magnet and for making connection to a terminal a contact of the rheostat.

13. In a rheostat, a controlling arm, a mag net for retaining said arm, and a single metal piece for forming the poles of said magnet and for making connection to a terminal and to a contact of the rheostat,

- 14-. In a rheostat, a controlling arm, a.

magnet for retaining said am, and a single sheet metal piece for forming the poles of said magnet and for making connection to a terminal an to a contact of the rheostat.

15. In a rheostat, a controlling contact arm, and, a single spring for retracting the arm to initial position and for cushioning the arm when thrown to initial position.

1:6. In a rheostat, a controlling arm, a spr ng for retracting the arm to initial position, a stop against which one portion of said springs seats, and a second stop against which another portion of said spring strikes when the arm is returned to initial position.

lit. In a rheostat, a controlling arm, a spring for returning the arm to initial nosition, a single piece having an abutment agamst WlllCh one portion of said snring seats, and said piece having a second abutment against which another portion of said spring strikes when the arm is returned to initial position. I

18. In a rheostat, a series of resistance contacts, a contact arm, a carrier pivotallr mounted on the inner side of said arm, and a contact carried by said carrier and movable inrelation thereto. 4

19. in a rheostat, a series oi resistance contacts, a contact arm, a carrier pivotally mounted on the inner side of said arm, a spring for pressing said carrier toward the face plate of the rheostat, and a contact carried. by said carrier and movable with relation thereto,

LEONARD KEBLER 

